Turbofan Fan Actuation With Pneumatic-Hydraulic Fail-Safe Packaging
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Solution Overview
Problem
The challenge of designing a fan actuation system for turbofan engines that accommodates a larger number of blades within a limited space while handling higher loading and compactness requirements, distinct from turboprop engines, is addressed by developing a compact and efficient fan actuation system that includes a hydraulic system with a pressurized pneumatic chamber for fail-safe operation and a unique relationship between the number of fan blades, fan tip diameter, and cruise Mach number to optimize packaging and loading.
Innovation Solution
A fan actuation system for turbofan engines utilizing a hydraulic system with a pressurized pneumatic chamber to ensure fail-safe operation and a relationship (FAS envelope) that considers the number of fan blades, fan tip diameter, and cruise Mach number to optimize packaging and loading, eliminating the need for counterweights and pitch lock devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a fan actuation system is designed for turbofan engines with a larger number of blades, then the loading capacity is improved, but the space requirement increases
Solution Approach 1:
The patent implements a nested configuration where the hydraulic piston is positioned within the fan hub, and the pneumatic chamber is integrated into the hydraulic system structure. This nesting approach allows the actuation system to accommodate more blades and handle higher loading while maintaining a compact footprint within the limited space available in turbofan engines.
Solution Approach 2:
The patent employs a hydraulic system with a pneumatic chamber to provide the necessary actuation force for controlling fan blades. The pneumatic-hydraulic combination enables the system to generate sufficient force for higher loading capacity while maintaining a compact design, resolving the contradiction between force requirements and space constraints.
2Device complexity
If counterweights and pitch lock devices are eliminated, then the device complexity is reduced, but the reliability may be compromised
Solution Approach 1:
The patent implements a self-service mechanism where the hydraulic system with integrated pneumatic chamber provides both the actuation force and the fail-safe positioning for fan blades. The system uses its own hydraulic pressure and pneumatic spring force to maintain blade position without requiring external counterweights or pitch lock devices, thereby reducing complexity while maintaining reliability through self-contained functionality.
Solution Approach 2:
The pneumatic chamber provides beforehand cushioning by storing potential energy in a compressed state, which can be released to maintain fan blade position in the event of hydraulic system failure. This prior cushioning mechanism ensures reliability without requiring additional complex safety devices like pitch lock devices.
3Area of stationary object
If the fan actuation system is made more compact, then the space requirement is reduced, but the loading capacity may be compromised
Solution Approach 1:
The patent uses a pneumatic-hydraulic system that combines the high energy density of pneumatic springs with the high force output capability of hydraulic pistons. This combination enables the system to achieve both compactness and high loading capacity, as the pneumatic chamber provides space-efficient force storage while the hydraulic system delivers the necessary actuation force for handling multiple fan blades.
Solution Approach 2:
The patent optimizes system parameters including the volume of the pneumatic chamber, the pressure differential across the hydraulic piston, and the mechanical advantage ratios to achieve the desired balance between compactness and loading capacity. By carefully adjusting these parameters, the system maintains high force output in a reduced space footprint.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a compact and efficient fan actuation system that meets the higher loading and space constraints of turbofan engines, ensuring reliable operation and reduced complexity, weight, and cost, while maintaining aerodynamic performance.
Implementation Method 1
a hydraulic system with a pressurized pneumatic chamber for fail-safe operation
Data Source
AI summary
A turbofan engine includes a fan and a fan actuation system. The fan has a plurality of fan blades. Each of the plurality of fan blades is rotatable about a pitch axis. The fan actuation system includes one or more actuators for rotating the plurality of fan blades about the pitch axis and one or more thrust bearings. The fan actuation system is characterized by a fan actuation system envelope in a range of 300 to 1860. The fan actuation system envelope is given byNFB×DFT×Mcruise(RTBNFB),where NFB is a number of the plurality of fan blades, DFT is a fan tip diameter of the plurality of fan blades, Mcruise is a Mach number of the turbofan engine at cruise operating conditions, and RTB is a thrust bearing radius of the one or more thrust bearings.